83 911 SC - Cruise Servo Testing - Need Help

[red83sc]

If someone be so kind and knows the specific servo vacuum test procedure, and post a reply it would be much appreciated. I've had a slow decrease in speed for years when CC engaged and I'm finally getting back to it. I sent the brain away way back and it was repaired. The car has a slow decrease in speed (10 mph over 7 miles) and i'm trying to figure out whether its the vacuum lines leaking to the servo or the servo itself. So far I've put vacuum to the servo 3 times, 10 vacuum and its held 8 minutes, 6 minutes & 5 minutes to zero. This is with no power to it. I read on here that you have to put power to it when testing ? Anyway, i'm hoping to find out how much vacuum holding for how long, power when testing or not, does the servo need to be removed and put on a bench or would an external 9 or 12 v power supply work while still in car when testing ect.
Thanks for the help and all replies appreciated !

[mysocal911]

Originally Posted by red83sc

If someone be so kind and knows the specific servo vacuum test procedure, and post a reply it would be much appreciated. I've had a slow decrease in speed for years when CC engaged and I'm finally getting back to it. I sent the brain away way back and it was repaired. The car has a slow decrease in speed (10 mph over 7 miles) and i'm trying to figure out whether its the vacuum lines leaking to the servo or the servo itself. So far I've put vacuum to the servo 3 times, 10 vacuum and its held 8 minutes, 6 minutes & 5 minutes to zero. This is with no power to it. I read on here that you have to put power to it when testing ? Anyway, i'm hoping to find out how much vacuum holding for how long, power when testing or not, does the servo need to be removed and put on a bench or would an external 9 or 12 v power supply work while still in car when testing ect.
Thanks for the help and all replies appreciated !

The servo is rarely the problem! The voltage connection is used to release the vacuum and disengage the operation.
The circuit board is 97% of the problem. Most likely your "rebuilder" didn't do a good job. Who did it?

[red83sc]

Hi Dave, Thanks for getting back to me. The work was done by a company called "cruise control repair and vintage restorations". This company seemed to know what they were doing, very nice fellow. Of note - when i received it back there was no change to the slow decline in speed. I was thinking of resending it back for another check. Before i spent more $ though i'm following up on the servo though to rule things out. To this point i haven't been able to find the servo vacuum holding spec. All thoughts appreciated.